202 PETROLOGY. 



obsidian, &c. AH these structures are shown to be the result of con- 

 traction. T. Gr. B. 



Bof icky, Dr. Em. retrographische Studien an den Melaphyrgcstcincn 

 Bohmens. [Bohemian Melaphyros.] Arch. nat. Land. Bblmi. Bd. 

 iii. Abth. 2, Heft 2, pp. 1-84 ; 2 chrome, pis. 

 Hornblende is almost entirely absent in the Bohemian melaphyros, 

 while orthoclase is sometimes equal in amount to the plagioclase. The 

 felspars are the predominant constituent, seldom falling below 50 p. c; 

 this distinguishes them from the felspar-basalts, where augite is the 

 chief element. Examples are grouped first according to the proportions 

 of mono- or triclinic felspar, and subdivided by their richness or poTerty 

 in augite, &c. Chemical analyses are adduced to supplement the optical; 

 and thereby their composition is arrived at : e. g. the Trosky rock con- 

 tains — andesine 55 p. c, augite 13, magnetite 10, olivine 3, apatite 1, 

 silica, alumina, &c. 18 p. c. Chapters on secondary minerals, &c. follow. 



E. B. T. 



Bouve, Th. T. On the origin of Porphyry. Proc. Boston Soc. Nat, 

 Hist. vol. xviii. p. 217. 



Bruton, J. B. Testing for Water in Coals. Iron, n. s. vol. viii. 



p. 328. (Amer. Inst. Min. Eng.) 

 Describes methods of analyses, and the amount of water found in 

 various samples. 



Calderon, Salvador. Eeseiia de las llocas de la Isla Yolcanica Gran 

 Canaria. [Bocks of the Volcanic Island of Grand Canary.] Pp. 

 33. 8vo. Madrid. 

 The same as the paper noticed in the Geological Becord for 1875, 

 p. 144. 



Cavazzi, A. Puzzuolana of St. Paul in Rome, and that of Maremma 

 in Tuscany. Ing. Civ. Artl Indust. vol. xxiv. p. 50. (Abstract 

 iu Froc. Inst. Civ. Eng. vol. xlvi. pp. 3G3-365.) 



Analyses given. 



Cohen, Dr. E. Yorliiufige Notiz iiber ein massenhaftes Vorkommen 

 basischer Gceteinsglaser. [Vitreous basic Bocks in Mass.] A". 

 Jahrh. Heft vii. pp. 744-747. 



A description of several lavas from the Sandwich Islands, which are 

 believed to occur in mass, and not subordinately as enclosures or as 

 salbands. They are basic, containing about 53 p. c. of silica, and are 

 in part very vesicular. They consist of an apolar vitreous matrix, with 

 crystals of plagioclase, augite, and olivine ; associated in some speci- 

 mens with concretionary structures, which present an opaque nucleus 

 surrounded by a translucent fibrous anisotropic rind. E. W. B. 



. Uebcr die sogenannten Hypersthenite von Palm a. [The so- 

 called Hypcrsthenites of Palma.] N. Jahrh. Heft vii. pp. 747- 

 752. 



